1. Field of the Invention
The present invention relates to a mass flow controller and a managing method of the same, and in particular to a mass flow controller for a control purge and a managing method of the same which are capable of implementing two functions of a common control function and purge function by one mass flow controller by automatically adjusting a gain proper to a small flowing amount and large flowing amount based on a set value of a gas flow inputted by a worker.
2. Description of the Background Art
Generally, a mass flow controller is directed to accurately and correctly adjusting the flowing amounts of various gases used for a fabrication of a semiconductor.
At this time, almost mass flow controllers adapt a sensor of a thermal conduction(thermal transfer method) which has the advantages that it is possible to directly measure a flowing amount of gas without changing a pressure or temperature, a high level electric output is possible, a small variation in gas flow is well detected based on its high sensitivity, and it has a small pressure loss and is well adapted to a wider pressure range.
FIG. 1 is a view illustrating a schematic construction of a conventional mass flow controller.
As shown therein, a mass flow controller 100 includes a thermal conduction type sensor 110, a bypass 120, a valve 130 and a control circuit 140.
The sensor 110 is implemented in such a manner that a detection coil is wound on a tube formed of a metallic material, etc. When a voltage is applied, the sensor is heated by a thermal sensitive resistance and detects a temperature difference occurring at both sides of a detection coil based on a flow of gas for thereby outputting the detected value to the control circuit 140.
The bypass 120 is adapted to flow a part of gas inputted from the outside to a tube in which the sensor 110 is installed and performs a function for dividing the flow of gas through a certain line which is separately connected in parallel with the sensor 110 and adjusting the ratio of the main flow line and the divided sensor flow line.
The valve 130 adjusts a flowing amount of gas in accordance with a control of a control circuit 140 which measures and controls an actual mass flow of gas flowing through the mass flow controller 100 based on the value of the temperature difference by a gas flow inputted from the sensor 110.
The control circuit 140 compares a set value inputted by a user with a value of the temperature difference based on a gas flow inputted from the thermal detection sensor 110 and controls the valve 130 for decreasing or increasing the flowing amount of gas based on a result of the comparison between the set value and the current mass flowing amount.
The operation of the mass flow controller 100 will be described. When a certain gas used for a fabrication of a semiconductor is inputted into the mass flow controller 100, the gas flow is divided before the gas is inputted into the bypass 120 and directly flows through the sensor 110. The sensor 110 detects a temperature variation between both sides of the detection coil based on the flow of a gas flowing through the tube and outputs a value of the temperature difference to the control circuit 140.
The control circuit 140 detects the current flowing amount of mass based on a value of the temperature difference inputted from the sensor 110 and compares the set value inputted by a user and a detected mass and controls the opening and closing operations of the valve 130.
Namely, in the case that the detected mass flowing amount is smaller than the set value inputted by the user, the valve 130 is more opened, and in the case that the detected mass flowing amount is larger than the set value inputted by the user, the valve 130 is closed. Therefore, the flow of the gas inputted through the bypass 120 is adjusted, so that a desired gas amount is outputted.
For example, in the case that the above described mass flow controller is used for a semiconductor etching process, two mass flow controllers, namely, a mass flow controller capable of accurately controlling the flowing amount of gas and a mass flow controller capable of performing a purge function(function for flowing a large flowing amount by opening a valve for a cleaning operation, etc.), are concurrently performed.
However, when the above mass flow controller is used for a semiconductor etching process, etc., since the common mass flow controller and purge mass flow controller must be concurrently used, there is an inconvenience for constructing the mass flow controller proper for each purpose. Therefore, the cost for the constructions of the equipment is high.